1. Technical Field
This invention is in the field of grain drying systems used with grain bins and, more particularly, a grain moisture regulating system employing ambient air blown into the bottom of the bin and moving upwardly through the grain mass when the outside air moisture content is less than the moisture content of the air within the grain bin.
2. Description of the Prior Art
Many examples of grain drying systems are found in the prior art, most of which employ some variation of the following described system. A perforated drying floor is suspended above the floor of the grain bin, and the grain mass rests on the drying floor. Air is directed under the drying floor and upwards through the grain mass by a fan unit or the like. As the directed air passes through the grain mass, the moisture on the outside of the kernels is "wiped off" and removed as the air exits the grain bin at the top thereof. The grain mass is thus slowly dried as air moves over the grain.
The prior art as thus described includes several disadvantages, one of the main ones being that the air used to dry the grain is sent through the grain mass regardless of the moisture content of the air. Clearly, if the air used for drying has a higher moisture content than the grain mass itself (which often occurs in grain-producing areas), the grain mass may actually be remoisturized which is counterproductive to the drying process. There is therefore a need for a drying system which will not operate when the outside moisture content is higher than the moisture content within the grain bin.
Another problem in the storage of grain occurs when grain is stored in the grain bin, the top of the grain mass often forms a dense top cap due to the moisture-bred "stickiness" of the upper grains. This top cap is often so dense that a man can walk on the top cap without his legs sinking into the top of the grain much beyond his shoe tops. In the prior art, when the fan is on, pressurized, moisture-laden air hits the empty void at the top of the bin above the grain mass, and there much of the moisture in the air falls back down when that air exits the bin exit ports because the ports release the air too quickly and the pressure at the top of the bin is too low. The result is an "air-stall".
Such an "air-stall" lets moisture be "rained" back out of the air mass which falls down onto the grain, clogging its air-flow and causing its top cap to get still more dense from expanded, moisture swollen kernels. The system hereof prevents much of the air stalling and "raining back" due to the generally continuous air flow under relative high pressure through the grain mass during the drying process. Such a process gives more drying opportunity for grain within the grain bin than those processes found in the prior art.
Drying efficiency in many prior art systems is decreased by static pressure, which in terms of the grain mass results from two major conditions. One involves the blocking of airflow by moistureswollen kernels, and the other involves air flow blockage by the tightly packed together kernels in the top cap.
Other prior art devices stir the dense top crust or top cap in grain bins by a mechanism sometimes called a "stir-ator". Such "stir-ators" can be quite expensive. There is therefore a need for a system which will act to substantially prevent formation of the top cap of the grain mass with or without a "stir-ator" unit being present.
One of the problems encountered in the prior art is that although some prior art systems determine the external humidity and others determine the internal humidity, there is no example in the prior art that discloses a system that will compare the external moisture content of the air to the internal moisture content and prevent fan operation for drying unless the external moisture content of the air is less than the internal moisture content. There is a need for such a system.
Another problem encountered in the prior art is that many of the drying systems presently being used steadily force relatively low volumes of air through the high moisture grain mass which can result in the redepositing of moisture on the top of the grain mass, the moisture that has been removed from the grain mass by the passage of air therethrough. As the warmed moisture-laden air travels upward through the grain and enters the upper region of the grain bin above the grain mass, unless there is sufficient air volume moving upwards through the grain mass, the moisture-laden air at the top of the grain bin is not forced out of the eave air outlets before it cools. As the air cools, it no longer can hold the same volume of moisture and some of the moisture will then recondense and fall out of the air on to the top of the grain mass. This can result in the formation of the top cap, which further acts to prevent drying of the grain mass. Such a condition can be prevented by moving larger masses of air through the grain mass. There is therefore a need for a drying system which will move greater amounts of air through the grain mass and prevent recondensation of water vapor from the air at the top of the grain bin.